1. Field of the Invention
The present invention relates to a multilayer capacitor that easily realizes a higher capacity as well as reduced ESL, and more particularly, to that suitable for use as a multilayer ceramic capacitor for achieving a high effect as a power source of a CPU.
2. Description of the Related Art
In recent years, due to an improved processing speed and a higher integration degree of a CPU (central processing unit) used for a data processor, its operating frequency is becoming higher and its current consumption is remarkably increasing. In accordance therewith, the operating voltage has been on the decreasing trend due to decreased power consumption. This has caused the occurrence of a higher-speed and larger current fluctuation in a power source for supplying power to the CPU, and it has become very difficult to control voltage fluctuation accompanying this current fluctuation within an allowable value range of this power source.
Therefore, as a measure for stabilizing the power source, a multilayer capacitor called a decoupling capacitor are frequently used in the state of being connected to a power source. By quick charge/discharge at the time of a high-speed transient current fluctuation, the multilayer capacitor supplies a current to a CPU, thereby reducing the voltage fluctuation of the power source.
However, today's trend toward a still higher frequency of the operating frequency of the CPU has resulted in higher-speed and larger current fluctuation. In accordance with consequent relative increase in equivalent series inductance (ESL) that the multilayer capacitor itself has, effective inductance has become larger. As a result, this equivalent series inductance gives a significant influence to the voltage fluctuation of the power source, so that it is not possible to respond to the future increase in processing speed of a CPU.
This is because that the voltage fluctuation at the time of the charge/discharge, in other words, at a current transient time, is approximated by the following expression 1, and the size of ESL is correlated with the magnitude of the voltage fluctuation.dV=ESL·di/dt  Expression 1where dV is voltage fluctuation (V) at the transient time, “i” is a current fluctuation amount (A), and “t” is a fluctuation duration (second).
Another conventional capacitor achieving ESL reduction by the structure such that a plurality of terminal electrodes are formed on a lower face which is on a substrate surface side of a multilayer body is concretely shown in FIG. 11 to FIG. 13(B), and a conventional multilayer capacitor 100 will be described below based on these drawings.
Specifically, the conventional multilayer capacitor 100 is structured such that two kinds of dielectric sheets 111, 112 having internal conductors 101, 102 and dielectric sheets 113 without any internal conductor formed thereon are stacked as shown in FIG. 11 to form a dielectric element 110, which is a multilayer body shown in FIG. 12, FIG. 13(A), and FIG. 13(B). Further, the multilayer capacitor 100 is structured such that a plurality of leadout portions 101A, 102A led out from the internal conductors 101, 102 on the dielectric sheets 111, 112 protrude to one face of the dielectric element 110.
The multilayer capacitor 100 is structured such that it includes a plurality of multilayer blocks 121 each formed of the dielectric sheets 111, 112 that have the internal conductors 101, 102, and multilayer blocks 122 each formed of the dielectric sheets 113 without any internal conductor and the multilayer blocks 121 are stacked alternately. As shown in FIG. 12 and FIG. 13(A), terminal electrodes 131, 132 are provided on an outer face of the dielectric element 110 to correspond to the leadout portions 101A, 102A, and these terminal electrodes 131, 132 are arranged so that the terminal electrodes adjacent to each other have different polarity from each other.
Therefore, as for the directions of currents flowing into the terminal electrodes 131, 132, the directions in the terminal electrodes adjacent to each other become reverse to each other when the multilayer capacitor 100 is mounted on a multilayer substrate 50 shown in FIG. 12, so that a magnetic flux canceling effect acts between the terminal electrodes adjacent to each other to reduce ESL. However, due to the existence of the plural multilayer blocks 122 that do not function as capacitors in the dielectric element 100, it is difficult for the multilayer capacitor 100 as structured above to have an increased capacity.